Water Diffusion-Weighted Breast MRI Might Reduce False-Positives and Biopsy Rates
The findings “show promise for using DW imaging to improve the specificity of breast MR imaging, reported senior author Savannah C. Partridge, PhD, of the Department of Radiology at the University of Washington School of Medicine in Seattle, Washington, and coauthors.
“DW imaging helped successfully characterize 46% of nonmalignant breast lesions assessed as false-positive findings at dynamic contrast-enhanced MR imaging,” they wrote.
Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is used in breast cancer diagnosis and staging, but suffers from a high rate of false-positive findings, necessitating frequent biopsying of suspect lesions.
But water diffusion-weighting of MRI data might improve the accuracy of DCE-MRI, the authors reasoned, if water diffuses differently between cells in malignant and benign breast lesions.
The new study examined DWI measurements of benign breast lesions in 165 women. The authors calculated DWI apparent diffusion coefficients (ADCs) for 175 lesions that had been identified with DCE-MRI as Breast Imaging Reporting and Data System category 4 or 5 lesions, but which were found to be benign after biopsy.
DWI correctly identified 81 (46%) of the false-positive lesions that had ADC values exceeding a predetermined threshold value, the authors reported. The most frequent subtypes among false-positive lesions with mean ADC values exceeding the threshold were fibroadenoma, focal fibrosis, normal tissue, aprocrine metaplasia, usual ductal hyperplasia, and inflammation.
“Fibroadenomas are generally presumed to have higher ADCs because of stromal myxoid change and consequent higher water mobility,” the authors reported. “This was confirmed by the relatively high ADC of the majority of fibroadenomas in our study; however, we also found that fibroadenoma represented the second most common dynamic contrast-enhanced MR imaging false-positive lesion subtype with ADCs below the threshold.”
High-risk atypical ductal hyperplasia and lobular neoplasia showed “significantly lower ADCs than other benign lesions (P < .0001) and were the most common lesions with ADCs below the threshold,” the authors reported.
Additional studies are needed to optimize the best use of ADC measurements for clinical breast MRI assessments, the authors emphasized.